1. Field of the Invention
The invention relates to the fields of mechanical engineering and thick-film technique and, more particularly, is directed to a process for the manufacture of PZT films of the type that are used in coating printing cylinders.
2. Description of the Prior Art
Thin films based on lead zirconate titanate (PZT) are conventionally fabricated on various substrate materials including Si, Al.sub.2 O.sub.3, ZrO.sub.2, and so forth. The thin PZT films are used for memory applications or for other scientific purposes, and can be produced by various methods. The significant methods for producing such PZT films are the sputtering method and the sol-gel method. Films produced in these methods have a thickness in the range of 1 .mu.m.
Thick films on substrate materials, such as Al.sub.2 O.sub.3 substrates, do not as yet exist, although they have been the focus of interest. It might even be said that the methods of thick-film technique cannot be applied to PZT batches for reasons grounded in the properties of PZT.
Two obstacles prevent the use of PZT in thick-film techniques. On the one hand, the traditionally high sintering temperatures of approximately 1200.degree. C. used when firing the films lead to a high lead oxide loss. This lead oxide loss tends to occur at the surface and leads to a complete change in the properties of PZT. On the other hand, difficulties arise due to the effect of transverse contraction. It is essential to the piezoelectric effect that an elongation is effected in the direction of polarization and in the field direction when voltage is applied. A transverse contraction occurs vertically to this effect. This means that the applied film contracts on the substrate, which can only take place within limits under conditions of firm adhesion. Forces resulting from this can be very large and lead to deformation of the substrate or chipping of the film.